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Remarkable life history polymorphism may be evolving under divergent selection in the silverleaf sunflower
Brook T Moyers1, Loren H Rieseberg1,2
1Department of Botany, University of British Columbia, 3529-6270 University Blvd, Vancouver, British Columbia, Canada, V6T 1Z4.
Molecular Ecology
|June 12, 2016
Summary
Silverleaf sunflowers show significant life history variation, with two distinct syndromes observed. This polymorphism suggests divergent selection may be driving ecological speciation in this species.
Area of Science:
- Evolutionary Biology
- Plant Ecology
- Speciation Research
Background:
- Intraspecific life history variation is uncommon and can indicate early ecological speciation.
- Geographically heterogeneous natural selection is a key driver of such variation.
- Helianthus argophyllus (silverleaf sunflower) is investigated for life history polymorphism.
Purpose of the Study:
- To report extensive life history polymorphism in Helianthus argophyllus.
- To examine evidence for the evolution of this polymorphism by divergent selection.
- To assess if this variation signals incipient ecological speciation.
Main Methods:
- 18 populations of Helianthus argophyllus were sampled across its range.
- Common garden experiments were used to assess quantitative traits.
- Genetic structure (FST) and phenotypic differentiation (QST) were compared.
Main Results:
- Two distinct life history syndromes were identified: tall/late-flowering and short/early-flowering.
- Phenotypic variation did not closely align with regional genetic structure.
- QST exceeded FST for key traits, indicating selection beyond neutral divergence.
Conclusions:
- Divergent selection is likely driving life history differences in Helianthus argophyllus.
- The observed patterns suggest early stages of ecological speciation.
- Silverleaf sunflower serves as a model for studying the initial phases of speciation.
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